As scores of fires continued to burn the length of eastern Australia today, a remarkable survival story emerged from Tasmania, where five young children escaped a blaze that destroyed about 90 properties in their village by sheltering under a boat jetty with their grandparents.

Tim and Tammy Holmes were looking after the children in the fishing village of Dunalley last Friday when they noticed smoke rising from a nearby ridge. Not long afterwards, “we saw tornadoes of fire just coming across towards us,” said Mr Holmes, 62. “The next thing we knew, everything was on fire all around us.”

Sending his wife and grandchildren, aged between two and 11, running down to the jetty, “because there was no other escape”, he paused only to send a message to his daughter – the children’s mother, who was at a funeral in Hobart that day – before sprinting past the flames to join them.

For two-and-a-half hours, the family huddled beneath the jetty, up to their necks in water, gulping mouthfuls of increasingly toxic air. “There were times when we had to move deeper because it was too hot, and there were times when the jetty itself caught fire,” he told Australia’s ABC Radio. With smoke and embers swirling around them, “there was probably only about 200-300mm of air above the water”.

Eventually Mr Holmes found a dinghy and dragged everyone about 300 yards out to sea, where the air was cleaner. The children’s mother, Bonnie Walker, was beside herself with worry. All she knew was that they had left the house and were “surrounded by fire”. She told ABC TV: “I braced myself to lose my children and my parents.”

The family was reunited the following day. The children’s father had no idea of the danger they had faced, as he had gone hiking in a remote area.

Mr and Mrs Holmes lost their house. “It’s all gone, every last item, but it’s a great sense of relief to think that we lost not one hair on a child’s head,” Mr Holmes said.

Today brought a welcome cool change to south-eastern Australia, but 200 fires still raged, from Tasmania in the south to the Gulf Country in the north-east.

In the south, firefighters battled to bring the blazes under control before the return of hot, windy weather on Friday. The extreme heat has moved up to northern and central Australia. With another week of heat forecast, there have been warnings that the bush fire emergency is far from over.

The past week has seen four of Australia’s 10 hottest days on record. David Jones, manager of climate monitoring at the Bureau of Meteorology, told Associated Press: “There’s little doubt that this is a very, very extreme heatwave event. If you look at its extent, its duration, its intensity, it is arguably the most significant in Australia’s history.”